Mucinous Adenocarcinoma of the Lung Diagnosed by Radial Endobronchial Ultrasound-guided Bronchoscopic Cryobiopsy and Presenting as Interstitial Lung Disease in a Patient with Systemic Sclerosis.

We report a patient with systemic sclerosis who was diagnosed with advanced-stage mucinous adenocarcinoma of the lungs. The clinical presentation, imaging findings, pathological results, and molecular diagnoses are presented. A 64-year-old woman with systemic sclerosis was administered prednisolone and hydroxychloroquine sulfate to control her disease. High-resolution computed tomography (HRCT) revealed an interstitial pattern in both lungs during annual imaging. Connective tissue disease-associated interstitial lung disease (CTD-ILD) was diagnosed using blood tests, pulmonary function tests, and imaging findings. One year later, the patient underwent follow-up chest HRCT, which showed progressive lung disease. The patient underwent endobronchial ultrasound (EBUS)-guided transbronchial lung cryobiopsy and computed tomography-guided biopsy for a pathological diagnosis. The pathology reports of bilateral lungs disclosed mucinous adenocarcinoma. After tumor staging and mutation testing, the patient received chemotherapy with pemetrexed and cisplatin. The bilateral lung lesions subsided after four cycles of first-line chemotherapy. Patients with CTD and lung involvement may be diagnosed with CTD-ILD. Although histopathological results are not mandatory for ILD diagnosis, EBUS-guided transbronchial lung biopsy or lung cryobiopsy should be considered when ILD has atypical or unexplained features.